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SDRAM is my friend

I read a lot of blogs about people doing hardware work just as I like to do. A long time ago a person who I have the utmost respect for failed to create a SDRAM (or DRAM, I can't really recall) controller which made me sure that I wouldn't be able to do it.

In order to continue with OpenRISC I will need some sort of big RAM, and after a slight nudge from a friend of mine I began reading about the SDRAM my DE2 board ships with.

Two days of tinkering produced this ugly (but working!) FSM. It is locked to using row 0x0 but writes a pattern to each column address (there are 256 of them on this SDRAM). After the write it will jump to a read / refresh loop which basically proves that it is capable of holding on the data.

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